Rivetless chains consist of alternating units of central links and pairs of side links joined together by headed pins. Each center link consists of an individual piece of metal having a pair of laterally spaced side walls joined at their end by curved end walls, the side walls and end walls enclosing or surrounding an elongated slot. A pair of side links, each having an elongated slot at each end, is pivotally connected to each end of each center link by headed pins, each pin having a transverse head on each end thereof. The side links are formed at their ends with transversely extending recesses on their outer faces in which the heads of the pins are seated to lock the pin in position after the center links and side links have been coupled together. Each of the center links has a narrow central portion that tapers outwardly adjacent to the ends of the link to form thickened portions at the link ends. When the center links and side links are assembled by means of the headed pins to form a chain, its center links and side links are arranged in alternate relationship along the chain, each center link having connected to each end thereof a pair of face side links and each such pair of side links being connected at each end to an adjacent center link and so that pivotal movement is permitted between the adjacent center links and side links about the center of headed pin as an axis.
Bar loop chains are similar in structure to the rivetless chains. However, with a bar loop chain, the pin is secured in the seated position with a nut or other fastener, thus preventing the unwanted disassembly of the chain. The side links correspondingly lack the longitudinally extending recesses of the rivetless chain.
Rivetless chains and bar loop chains are preferred in many trolley type manufacturing settings since they will not readily collapse and can be easily adapted for use with a sprocket gear drive. Trolley systems are generally used in animal processing plants in order to ease the movement of carcasses between various stages of the processing procedure. The carcass is generally attached to an overhead trolley that transports the carcass along an endless defined path to the various processing stations. Trolleys are generally propelled along the endless path by either gravity, or by a motorized chain or cable.
Processors were unable to use lubricants on the trolley systems and chains due to possible contamination of the carcass from the lubricating oils. This resulting friction between the chain and the trolley system, and internal friction between the chain links and the retention pin caused frequent breaks in the chain due to fatiguing of the parts. The processing line would then have to be stopped while the chain was repaired.
Since lubricants could not be used on the chains, processors simply accepted these frequent chain breakages as a business cost. However, with the approval of H1 food grade lubricants, work stoppages due to broken chains can now be decreased. Lubricating oil can now be used on trolley systems and chains used in food processing plants.
U.S. Pat. No. 5,966,923 issued to Nakamura discloses a chain wherein lubricating oil is fed into a U-shaped or V-shaped recess in the connecting pin. Viscosity of the oil adheres it to the pin and prevents its immediate flow down the surface of the pin. As the chain moves, the lubricating oil then gradually flows down the pin, and providing continuous lubrication to the chain.
U.S. Pat. No. 5,078,654 issued to Naz discloses a center link for a rivetless chain. The center link has an integrally formed reservoir and lubricator for holding and distributing lubricant to connector pins between adjacent center links and side bars. The reservoir is an impression in the curved end wall portions having an arcuate concave surface in the end wall portion. It is designed to accept and hold a desired amount of lubricant from a source. The lubricant is then distributed to the connector pins through normal chain movement.
Despite the improvements described, a need remains for improvements to self-lubricating chains, especially in the food processing industry. H1 graded lubricants may not work well with the self-lubricating chains described above, which rely on viscosity of the lubricating oil for proper function. Furthermore, there is always a desire to reduce the machining costs of the self-lubricating chain links described in the prior art, or employ a center link that reduces the cost of such machining.
Accordingly, the present invention is an improved chain with improved side links which facilitate lubrication of connector pins of a rivetless or bar loop conveyor chain. From the following detailed description taken in conjunction with the accompanying drawings and following claims, further understanding of the present invention and its advantages will become apparent.